Fixation assembly and method of use

ABSTRACT

A fixation assembly for bone fixation and a method for joining bones or bone fragments of a single bone and translating uniform compression to the bones. The fixation assembly comprises a post member coupled to a screw member. The post member comprises a head portion connected to an anchoring portion, wherein the head portion is offset from the anchoring portion by a first angle. The head portion may comprise a curved body annularly extending from a first end to a second end, wherein the first end is separated from the second end by a slot, and wherein the curved body defines a tapered annular bore therein. The anchoring portion comprises a first leg extending from the first end of the curved body and a second leg extending from the second end of the curved body. The screw member comprises a tapered bulbous portion connected to a threaded elongated portion. The screw member is coupled to the post member by advancing the elongated portion of the screw member through the tapered bore of the post member until the tapered bulbous portion of the screw member abuts the tapered bore of the post member thereby creating an interference fit. The first angle of the post member determines the angle of fixation of the post member with respect to the screw member.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/385,624, filed on Apr. 16, 2019, which is a continuation of U.S.patent application Ser. No. 14/594,953, filed on Jan. 12, 2015. Theentire contents of those applications are incorporated herein byreference.

FIELD OF THE INVENTION

This invention relates to the field of implant devices, and moreparticularly, to a fixation assembly for joining bones by applyinguniform compression through multi-point fixation.

BACKGROUND OF THE INVENTION

Implant devices, such as intramedullary nails, plates, rods, screws,Kirschner wires (K-wires), and screw-and-washer assemblies are oftenused to repair or reconstruct bones and joints affected by trauma,degeneration, deformity, fractures, and disease, such as Charcotarthropathy caused by diabetes in some patients, Hallux Valgusdeformities, failed Keller Bunionectomies, Rheumatoid Arthritis,injuries, and severe deformities. Infections and wound complications area major concern in the aforementioned procedures. Wound closure istechnically demanding for the surgeon, and devices that add surfaceprominence, such as plates or exposed screws, add to the difficulty byrequiring greater tissue tension during incision reapproximation. Thisincreases the risk of postoperative wound infections and dehiscence thatmay ultimately result in limb amputation.

Various implants have been utilized for surgical treatment of thesebones and joints, including bone screws. Implants have also beenutilized to treat severe deformities in the metatarsal and phalangealbones, including multiple screws and plates. These multiple screws andplate implants have been commonly used in a first metatarsal-phalangealfusion procedure to fuse the first metatarsal to the first phalangealbone in hallux valgus deformities, failed Keller bunionectomies,rheumatoid arthritis, and other types of severe deformities in themetatarsal and phalange bones. While these devices allow fixation andpromote fusion, they do not deliver restoration of the arch in a Charcotfoot, they are not effective in metatarsal-phalangeal (MTP) fusionprocedures, nor do they deliver uniform compression for variouspredetermined angles of compression.

Particularly, screw implants in MTP procedures are ineffective indelivering sufficient compression to the bones in the foot, preventingscrew head break out, or delivering effective bending resistance.Moreover, hard to control dorsiflexion and valgus angles as well as skinirritation from proximity to the skin prevents these screw implants frombeing readily utilized for surgical treatment. Yet further, plateimplants used with bone screws too have the same drawbacks as fixedvarus and valgus angles, lack of direct compression across the MTPjoint, and skin irritations from proximity to the skin reduce theeffectiveness of these implants.

Still further, use of K-wires, screws, screw-and-washer assemblies, andplates for the reduction and internal fixation of arthrodesis,osteotomy, intra-articular and extra-articular fractures, and non-unionsof bones and joints of the hand, foot, arm, leg and various other bodyparts are ineffective in delivering the strength necessary to maintainsufficient reduction and/or fixation of the fractured bone, maximizingcortical bone contact, retaining bones in most anatomically correctposition, preventing screw head break out, minimizing the size of theincision(s) necessary to install the hardware, minimizing soft tissueand tendon disruption and/or displacement, stabilizing fixation of thefracture, easing mobility for the patient, and eliminating hardwareprofiles.

There is therefore a need for a fixation assembly and method of use thatovercomes some or all of the previously delineated drawbacks of priorfixation assemblies.

SUMMARY OF THE INVENTION

An object of the invention is to overcome the drawbacks of previousinventions.

Another object of the invention is to provide a novel and usefulfixation assembly that may be utilized to treat bones in a human body.

Another object of the invention is to provide a system for compressingbones using a fixation assembly.

Another object of the invention is to fuse bones through the use of anintraosseous assembly.

Another object of the invention is to provide a novel fixation assemblythat is securely assembled by securing a screw member to a post membervia a tapered connection or engagement.

Another object of the invention is to provide a fixed acute anglefixation assembly for bone fixation.

Another object of the invention is to provide a fixation assembly thatprovides sufficient strength, delivers a highly stable fixation, andmaintains reduction of a fractured bone.

Another object of the invention is to provide a fixation assembly thatmaximizes cortical bone contact.

Another object of the invention is to provide a fixation assembly thatfixates to the subchondral bone and/or the cortical bone.

Another object of the invention is to provide a fixation assembly thatretains and realigns bones in anatomically correct positions.

Another object of the invention is to provide a fixation assembly thatreduces and/or eliminates unnecessary hardware.

Another object of the invention is to provide a fixation assembly thatminimizes the size of the incision(s) necessary to install the fixationassembly.

Another object of the invention is to provide a fixation assembly thatminimizes soft tissue and tendon disruption and/or displacement.

Another object of the invention is to provide a fixation assembly thatallows for early post procedure mobilization of the patient.

Another object of the invention is to provide a fixation assembly thatreduces and/or eliminates hardware profiles.

Another object of the invention is to provide a method for the reductionand fixation of arthrodesis, osteotomy, intra-articular andextra-articular fractures and non-unions of bones and joints of thehand, foot, arm, leg and various other body parts.

In one embodiment of the invention, a fixation assembly for bonefixation is provided comprising a post member coupled to a screw member.The post member comprises a head portion connected to an anchoringportion, wherein the head portion is offset from the anchoring portionby a first angle. The head portion may comprise a curved body annularlyextending from a first end to a second end, wherein the first end isseparated from the second end by a slot, and wherein the curved bodydefines a tapered annular bore therein. The anchoring portion comprisesa first leg extending from the first end of the curved body and a secondleg extending from the second end of the curved body. The screw membercomprises a tapered bulbous portion connected to a threaded elongatedportion. The screw member is coupled to the post member by advancing theelongated portion of the screw member through the tapered bore of thepost member until the tapered bulbous portion of the screw member abutsthe tapered bore of the post member thereby creating an interferencefit. The first angle of the post member determines the angle of fixationof the post member with respect to the screw member. The fixationassembly of the present invention translates uniform compression tofirst and second bone segments (i.e., a first bone and a second bone, orfirst and second bone fragments of a single bone).

Broadly, the methods of the invention for joining and compressing afirst bone segment to a second bone segment comprises: creating a firsthole in the first bone segment and a second hole in the second bonesegment along a first longitudinal axis; creating a depression below thecortex of the first bone segment by removing bone material from thefirst bone segment; creating third and fourth parallel holes in thefirst bone segment along a second longitudinal axis; advancing the firstand second legs of the post member into the third and fourth parallelholes in the first bone segment; pressing the head portion of the postmember into the depression in the first bone segment; and advancing thescrew member through the bore of the post member and into the first holein the first bone segment and the second hole in the second bone segmentuntil the bulbous portion of the screw member abuts the bore of the postmember.

Instruments are also disclosed for use in practicing the invention.Numerous variations may be practiced in the preferred embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the invention can be obtained by reference toa preferred embodiment set forth in the illustrations of theaccompanying drawings. Although the illustrated embodiment is merelyexemplary of systems and methods for carrying out the invention, boththe organization and method of operation of the invention, in general,together with further objectives and advantages thereof, may be moreeasily understood by reference to the drawings and the followingdescription. The drawings are not intended to limit the scope of thisinvention, which is set forth with particularity in the claims asappended or as subsequently amended, but merely to clarify and exemplifythe invention.

For a more complete understanding of the invention, reference is nowmade to the following drawings in which:

FIG. 1 is a perspective view of a fixation assembly according to anembodiment of the invention;

FIG. 2A is a front perspective view of a post member of the fixationassembly shown in FIG. 1 according to an embodiment of the invention;

FIG. 2B is a front view of the post member shown in FIG. 2A according toan embodiment of the invention;

FIG. 2C is a rear view of the post member shown in FIG. 2A according toan embodiment of the invention;

FIG. 2D is a side view of the post member shown in FIG. 2A according toan embodiment of the invention;

FIG. 2E is a top view of the post member shown in FIG. 2A according toan embodiment of the invention;

FIG. 2F is a bottom view of the post member shown in FIG. 2A accordingto an embodiment of the invention;

FIG. 3A is a perspective rear view of a post member of the fixationassembly shown in FIG. 1 according to an alternate embodiment of theinvention;

FIG. 3B is a front view of the post member shown in FIG. 3A according tothe alternate embodiment of the invention;

FIG. 3C is a rear view of the post member shown in FIG. 3A according tothe alternate embodiment of the invention;

FIG. 3D is a side view of the post member shown in FIG. 3A according tothe alternate embodiment of the invention;

FIG. 3E is a top view of the post member shown in FIG. 3A according tothe alternate embodiment of the invention;

FIG. 3F is a bottom view of the post member shown in FIG. 3A accordingto the alternate embodiment of the invention;

FIG. 4 is a front view of a screw member of fixation assembly shown inFIG. 1 according to an embodiment of the invention;

FIG. 5A is a perspective view of an instrument used to couple thefixation assembly shown in FIG. 1 to the bones according to anembodiment of the invention;

FIG. 5B is a side view of the instrument shown in FIG. 5A according toan embodiment of the invention;

FIG. 5C is a top view of the instrument shown in FIG. 5A according to anembodiment of the invention;

FIG. 5D is a bottom view of the instrument shown in FIG. 5A according toan embodiment of the invention;

FIG. 5E is a rear view of the instrument shown in FIG. 5A according toan embodiment of the invention;

FIG. 5F is a front view of the instrument shown in FIG. 5A according toan embodiment of the invention;

FIG. 6 is a cross-sectional view of the instrument taken along line 6-6in FIG. 5C;

FIG. 7 is a flow chart depicting illustrative steps of a method ofcoupling the fixation assembly shown in FIG. 1 to bones according to anembodiment of the invention; and

FIGS. 8A-8F depict details of certain steps of FIG. 7 .

DETAILED DESCRIPTION OF THE INVENTION

The invention may be understood more readily by reference to thefollowing detailed description of preferred embodiment of the invention.However, techniques, systems, and operating structures in accordancewith the invention may be embodied in a wide variety of forms and modes,some of which may be quite different from those in the disclosedembodiment. Consequently, the specific structural and functional detailsdisclosed herein are merely representative, yet in that regard, they aredeemed to afford the best embodiment for purposes of disclosure and toprovide a basis for the claims herein, which define the scope of theinvention. It must be noted that, as used in the specification and theappended claims, the singular forms “a”, “an”, and “the” include pluralreferents unless the context clearly indicates otherwise.

Referring now to FIG. 1 , there is shown a fixation assembly 100 whichis made in accordance with the teachings of the preferred embodiment ofthe invention. As shown, the fixation assembly 100 includes a screwmember 102 adapted to be locked to a post member 101. Fixation assembly100 is used to translate intraosseous and uniform compression to bonesegments (i.e., a plurality of bones or a plurality of bone fragments ofa single bone) for treating and fusing deteriorated, damaged, orfractured bones in the human body. In particular, fixation assembly 100may be used for the reduction and internal fixation of arthrodeses,osteotomies, intra- and extrarticular fractures and nonunions of thesmall bones and joints of the foot and ankle. Fixation assembly 100preferably delivers the strength necessary to maintain sufficientreduction and/or fixation of a fractured bone, maximizes cortical bonecontact, retains bones in an anatomically correct position, preventsscrew head break out, minimizes the size of the incision(s) necessary toinstall the hardware, minimizes soft tissue and tendon disruption and/ordisplacement, stabilizes fixation of the fracture, eases mobility forthe patient, provides early post-operation mobilization of the fracturebone, and reduces and/or eliminates hardware profiles. Moreover,fixation assembly 100 generally provides a more stable and rigidfixation than the prior art because it is fixed to the strongest bonenear the fracture and because it redistributes the force normally placedon the head of a screw along the assembly.

For example, fixation assembly 100 may be used to join a first bone 105having a proximal end 107 and side surface 109 to a second bone 106having a distal end 108, and specifically, to join the proximal end 107of first bone 105 with distal end 108 of second bone 106. The fixationassembly 100 can be used to joint any bones of the hand and the foot, aswell as for internal fixation of any other bones in the human body,including, but not limited to, the talus and navicular bones in thetalonavicular joint, the calcaneus and cuboid bones in thecalcaneocuboid joint, the metatarsal and cuneiform bones in themetatarsocuneiform joints, the tibia and talus bones in the tibiotalarjoint, metatarsal osteotomies, as well as the metatarsals and thephalanges. The fixation assembly 100 may be further used to joint bonefragments of a single bone to treat bone fractures. It should beappreciated that screw member 102 and post member 101 of fixationassembly 100 may be provided at several sizes, lengths or widths, forthe internal fixation of a variety of bone sizes in the human body.

Post member 101 comprises an anchoring portion 104 aligned alonglongitudinal axis 110 extending along the length of post member 101 foranchoring post member 101 in bone 105. Post member 101 further comprisesa head portion 103 aligned along longitudinal axis 112 and offset fromthe anchoring portion 104 and longitudinal axis 110 at an angle A. AngleA determines the angle of fixation of post member 101 with respect tothe screw member 102. Angle A is provided at various angles depending onthe bone fragments that are being compressed. Angle A may be any angleless than 90 degrees and is preferably in the range of about 30 degreesto about 75 degrees. Screw member 102 is aligned along longitudinal axis111 and is fixed to the post member 101 at angle B. Angle B may be anyangle less than 90 degrees and is preferably in the range of about 15degrees to about 60 degrees. Angle B causes the fixation assembly 100 to“hook” into bones 105 and 106 and translate uniform compression appliedto the bones through multi-point fixation. In particular, fixationassembly 100 distributes compressive forces across a wide surface areaproviding orthogonal multi-plane fixation and bicortical cross screwfixation to bones. In a locked position, screw member 102 compressesbones 105 and 106, while the post member 101 acts as an intraosseousbicortical anchor, which lags bones 105 and 106 together in a parallelfashion in directions D1 and D2. Beneficially, fixation assembly 100maintains compression even if the cortical bridge of the bone iscompromised.

It should also be appreciated that the fixation assembly 100 isimplanted through a minimal incision and is provided to be substantiallywithin the bone (i.e., intraosseous), thereby reducing the disruption tothe plantar tissues while at the same time minimizing the tension on theskin. This allows for improved wound closure, reduced operating roomtime, reduction in the number of incisions required, and reduction inthe total length of incisions. Fixation assembly 100 may also beutilized with graft material (i.e., autograft, allograft or otherbiologic agent). Furthermore, it should be appreciated that a pluralityof fixation assemblies, such as fixation assembly 100, may be insertedinto any of the bones of the body, such as but not limited to, radial,humerus, tibia, and femur, in order to fixate fractures, withoutlimiting the scope of the invention. For example, the orientation offixation assembly 100 and method of use may be utilized to fixate adistal radius fracture by rigidly fixating two fixation assemblies 100to the subchondral bone and/or cortical bone and applying acute anglecompression to the fracture. This orientation and method of usemaintains reduction of the fracture by realigning the bone to itsnatural anatomical position, which allows for quicker healing time andearlier mobilization of the patient.

Post member 101 of fixation assembly 100 is shown in greater detail inFIGS. 2A-2F, where FIG. 2A is a front perspective view of the postmember 101, FIG. 2B is a front view thereof, FIG. 2C is a rear viewthereof, FIG. 2D is a side view thereof, FIG. 2E is a top view thereof,and FIG. 2F is a bottom view thereof. Post member 101 preferablycomprises unitary elongated body 200 extending from a first end 206 to asecond end 207. Post member 101 is aligned along longitudinal axis 110,which is longitudinally coextensive the length of post member 101. Postmember 101 may be made of materials known in the art, includingtitanium, titanium alloy, stainless steel, cobalt chrome, PEEK, andresorbable polyactic acid (PLA). Also, post member 101 may be coatedwith an osteoconductive material, such as, for example, plasma spray orother similar types of porous materials, that are capable of supportingor encouraging bone ingrowth into the material. It should be appreciatedthat the length of the post member 101 may be selected of varyinglengths to allow a surgeon to fuse different joints in the human body.

Post member 101 comprises a head portion 103 at its first end 206 fixedto an anchoring portion 104 at its second end 207. Head portion 103 isaligned along longitudinally axis 112 and is offset from the anchoringportion 104 and longitudinal axis 110 by angle B. Angle A determines theangle for fixation of post member 101 with respect to the screw member102 at angle B (shown in FIG. 1 ). Angle A is provided at various anglesdepending on the bone fragments that are being compressed. Angle A maybe any angle less than 90 degrees and is preferably in the range ofabout 30 degrees to about 75 degrees. Head portion 103 preferablycomprises a curved body 213. However, head portion 103 may comprise anyother shape including a rectangular shape or a non-uniform shape. Curvedbody 213 annularly extends from a first end 216 to a second end 217,separated by a slot 214. Curved body 213 has an annular bore 212, whichtraverses head portion 103 through its width and extends from a frontface 210 to a rear face 211 of head portion 103 along longitudinal axis111 (shown in FIG. 1 ). Bore 212 annularly extends from a first end 216to a second end 217, wherein the first end 216 is separated from thesecond end 217 by slot 214. Bore 212 is sized and shaped to receive ahead of screw member 102 as is shown in FIG. 1 . Bore 212 preferablycomprises an inner wall 215 having a taper. Bore 212 tapers from frontface 210 to rear face 211—i.e., bore 212 has a diameter that decreasesfrom front face 210 to rear face 211. In a preferred embodiment, bore212 comprises a Morse taper.

Anchoring portion 104 is adapted to be fixed transversely to a bone or abone fragment as will be later described. Anchoring portion 104comprises a first leg 201 and a second leg 202 extending alonglongitudinal axis 110. First leg 201 extends from the first end 216 ofcurved body 213 to second end 207 of post member 101 and second leg 202extends from the second end 217 of curved body 213 to second end 207 ofpost member 101. First and second legs 201 and 202 are preferablysubstantially parallel and substantially cylindrical in shape. First andsecond legs 201 and 202 may comprise other shapes. For example, firstand second legs 201 and 202 may comprise a rectangular cross-section, ora semi-circular cross-section as shown in FIGS. 3A-3F. Each of the firstand second legs 201 and 202 preferably has a smooth exterior surface andcomprises a substantially uniform diameter. Alternatively, first andsecond legs 201 and 202 may comprise a taper. First and second legs 201and 202 of the post member 101 create a wide profile across first bone105 because the first and second legs 201 and 202 are offset withrespect to one another. The wide profile assists in providing abetter-secured anchor. First and second legs 201 and 202 preferablyterminate at first and second tips 221 and 222, respectively. Each ofthe first and second tips 221 and 222 may comprise a conical shapeterminating at a point for ease of insertion of legs 201 and 202 intothe bone. First and second tips 221 and 222 may comprise other shapes,as shown for example in FIGS. 3A-3F.

FIGS. 3A-3F illustrate an alternative embodiment of post member 300,where FIG. 3A is a perspective rear view of the post member 300, FIG. 3Bis a front view thereof, FIG. 3C is a rear view thereof, FIG. 3D is aside view thereof, FIG. 3E is a top view thereof, and FIG. 3F is abottom view thereof. Post member 300 preferably comprises unitaryelongated body 320 extending from a first end 306 to a second end 307.Post member 300 comprises a head portion 303 at its first end 306 fixedto an anchoring portion 304 at its second end 307.

Head portion 303 comprises a curved body 313 annularly extending from afirst end 316 to a second end 317, separated by a slot 314. Curved body313 has an annular bore 312, which traverses head portion 303 throughits width and extends from the front face 310 to the rear face 311 ofhead portion 303. Bore 312 is sized and shaped to receive a head ofscrew member 102 as is shown in FIG. 1 . Bore 312 preferably comprisesan inner wall 315 having a taper, which tapers from front face 310 torear face 311 (i.e., bore 312 has a diameter that decreases from frontface 310 to rear face 311). In a preferred embodiment, bore 312comprises a Morse taper.

Anchoring portion 304 is adapted to be fixed transversely to a bone or abone fragment as will be later described. Anchoring portion 304comprises substantially parallel first and second legs 301 and 302.First leg 301 extends from the first end 316 of curved body 313 tosecond end 307 of post member 300 and second leg 302 extends from thesecond end 317 of curved body 313 to second end 307 of post member 300.First and second legs 301 and 302 comprise a semi-circular cross-sectionas shown in FIG. 3F formed by partially-flat front-facing surfaces 326and 327, oppositely disposed partially-flat rear-facing surfaces 328 and329, flat outer-facing surfaces 324 and 325, and curved inner-facingsurfaces 330 and 331. First and second legs 301 and 302 may comprise aplurality of barbs 334 and 335 extending transversely from thepartially-flat rear-facing surfaces 328 and 329. Alternatively, theplurality of barbs 334 and 335 may be disposed on partially-flatfront-facing surfaces 326 and 327, oppositely disposed flat outer-facingsurfaces 324 and 325, curved inner-facing surfaces 330 and 331, or anycombinations thereof. In addition, the plurality of barbs 334 and 335may be disposed around the entire circumference of first and second legs301 and 302. The plurality of barbs 334 and 335 are used to buttresslegs 301 and 302 against the bone. First and second legs 301 and 302preferably terminate at first and second tips 321 and 322, respectively.Each of the first and second tips 321 and 322 may taper from oppositelydisposed flat outer facing surfaces 324 and 325 to curved inner facingsurfaces 330 and 331, terminating at a point for ease of insertion oflegs 301 and 302 into the bone.

As shown in FIG. 4 , screw member 102 comprises a unitary elongated body400 extending from a first end 403 to a second end 404 alonglongitudinal axis 111. Screw member 102 may be made of materials knownin the art, including titanium, titanium alloy, stainless steel, cobaltchrome, PEEK, and resorbable polyactic acid (PLA). Also, screw member102 may be coated with an osteoconductive material, such as, forexample, plasma spray or other similar types of porous materials, thatare capable of supporting or encouraging bone ingrowth into thematerial. It should be appreciated that the length of the screw member102 may be selected of varying lengths to allow a surgeon to fusedifferent joints in the human body.

Screw member 102 comprises an elongated portion 401 connected to abulbous portion 402. The elongated portion 401 is substantiallycylindrical in shape with a substantially uniform diameter. However,elongated portion 401 may be tapered from the bulbous portion 402 to thesecond end 404 of the screw member 102. Elongated portion 401 preferablycomprises threads 412, such as helical threads, which arecircumferentially disposed on the exterior surface 410 of the elongatedportion 401. It should be understood that any commonly used threads forengaging and coupling may be used without limiting the scope of theinvention. Elongated portion 401 may also be provided with aself-tapping leading edge 409 to provide elongated portion 401 with theability to remove bone material during insertion of screw member 102into bone.

Bulbous portion 402 preferably comprises a taper, such as a Morse taper,on its outer surface 411 with a diameter that decreases from first end403 of the screw member 102 to the elongated portion 401. The taper ofbulbous portion 402 allows for a locked interference fit with taperedbore 212 (shown in FIGS. 2A-2F) when tapered bulbous portion 402 resideswithin tapered bore 212, as shown in FIG. 1 .

Moreover, bulbous portion 402 is substantially cylindrical in shape andhas an aperture 407 aligned along axis 111 traversing the longitudinallength of bulbous portion 403. Aperture 407 is provided to receive aninstrument (not shown) for applying torque to screw member 102. Aperture407 may comprise any shape known in the art, including, ahexagonal-shaped aperture, a star-shaped aperture, a square-shapedaperture, or any other shaped aperture may be utilized without departingfrom the scope of the invention.

Screw member 102 is preferably cannulated along its longitudinal lengthhaving a bore 406 that traverses the screw member 102 along longitudinalaxis 111 and extending from the first end 403 to the second end 404.Bore 406 is provided to interact with a guide wire or a Kirschner wire(K-wire) by receiving the K-wire within the bore 406 to help guide andposition the screw member 102 into the bone as will be later described.Preferably, the diameter of bore 406 is constant throughout the lengthof the screw member 102. Different diameters and K-wire sizes may beused depending on the diameter of the bones that are being joined andthe surgeon's preferences. Illustratively, the diameter of the K-wire isin the range of approximately 0.7 to 4.0 millimeters (mm), and morepreferably approximately 0.9 to 1.6 mm. In another embodiment, screwmember 102 may be provided without a bore 406 (i.e., the screw member102 may be solid).

FIGS. 5A-5F illustrate a preferred embodiment of an instrument 500 usedto couple the fixation assembly 100 to the bones. FIG. 5A illustratesthe perspective side view of the instrument, FIG. 5B illustrates a sideview thereof, and FIG. 5C illustrates the top view thereof, FIG. 5Dillustrates the bottom view thereof, FIG. 5E illustrates the rear viewthereof, and FIG. 5F illustrates the front view thereof. FIG. 6illustrate the cross-section of the instrument taken along line 6-6 inFIG. 5C. Instrument 500 comprises a unitary elongated body 501.Elongated body 501 includes a handle portion 502 extending from a firstend 511 to a second end 512 and aligned with its length alonglongitudinal axis 510. Handle portion 501 may be ribbed (not shown) ormay comprise friction resistant material to assist the surgeon tomanually apply torque to the instrument 500. Alternatively, or inaddition, handle portion 501 may be sized to receive a torquetransmitting tool (not show).

Elongated body 501 further comprises a head portion 503 coupled to thehandle portion 502. Head portion 503 extends from a first end 513 to asecond end 514 and is aligned with its length along longitudinal axis515. Head portion 503 and handle portion 501 are coupled at theircorresponding first ends 511 and 513. Head portion 503 and therebylongitudinal axis 515 is offset from the handle portion 502 and therebyoffset from the longitudinal axis 510 by angle C. Angle C may be anyangle less than 90 degrees and preferably it is substantially equivalentto angle B. As such, angle C is preferably in the range of about 15degrees to about 60 degrees. Head portion 503 preferably comprises anoval cross-section transverse to longitudinal axis 515. Head portion 503further comprises a pair of parallel bores 505 and 506 that traversehead portion 503 along longitudinal axis 515 from the first end 513 tothe second end 514. In a preferred embodiment, bores 505 and 506 aresized, shaped, and spaced-apart to correspond to first and second legs201 and 202 of post member 101. Preferably bores 505 and 506 aresubstantially cylindrical in shape with a substantially uniformdiameter. Head portion 503 further comprises a rasp portion 520extending transversely from its front end 513. Rasp portion 520comprises a plurality of teeth 521 arranged in fan-like configuration.Teeth 521 are used to clear bone material as will be later described. Ina preferred embodiment, the front surface of rasp portion 520 is alignedalong longitudinal axis 516. Front surface of rasp portion 520, andthereby longitudinal axis 516, are offset from the pair of parallelbores 505 and 506, and thereby from longitudinal axis 515, by angle D.Preferably angle D is substantially equivalent to angle A. As such,angle D may be any angle less than 90 degrees and is preferably in therange of about 30 degrees to about 75 degrees. As shown in FIG. 6 ,instrument 500 is cannulated having a bore 508 extending alonglongitudinal axis 510 of handle 502 from a first end 511 to a second end512.

The fixation assembly 100 of the present invention is utilized to jointwo bones or two bone fragments together and to translate compressionbetween the bones. FIGS. 7 and 8A-8F depict illustrative operativetechnique of an embodiment of the invention used joint a first bone (orbone fragment) 105 to a second bone (or bone fragment) 106. It will beunderstood that the operative technique is only illustrative, that theorder of execution of some steps may vary, and that some steps may notneed to be used in the treatment of a particular patient in accordancewith the invention.

Initially, in step 710 an incision is made in the skin over first bone(or first bone fragment) 105 and second bone (or second bone fragment)106. The incision may be a dorsal longitudinal incision or a twosemi-elliptical incision. Next, in step 712 and as shown in FIG. 8A, aretrograde K-wire 805 is advanced diagonally into the side surface 109of the first bone 105 and through its proximal end 107. The K-wire 805is further advanced through the distal end 108 of the second bone 106.The K-wire 805 is advanced by the surgeon in a direction of the desiredalignment of the fixation assembly 100 with respect to the first andsecond bones 105 and 106. Then in step 714, as shown in FIG. 8B, thefirst and second bones 105 and 106 are drilled using drill bit 810 overthe K-wire 805 to create a first hole 811 in the first bone 105 and asecond hole 812 in the second bone 106. The K-wire 805 is used to guidedrill bit 810 into the desired alignment. Accordingly, the drill bit 810used in the present invention is preferably cannulated such that it mayfit over the K-wire 805. The drill bit 810 may be driven manually or viaa torque transmitting tool (not shown). Hole 811 extends from the sidesurface 109 to proximal end 107 of the first bone 105 and hole 812extends through the distal end 108 into the second bone 106.

In step 716, as shown in FIG. 8C, instrument 500 is advanced over theK-wire 805 by inserting the K-wire 805 inside the bore 508 of instrument500 until rasp portion 520 contacts the side surface 109 of first bone105. Rasp portion 520 is used to remove bone material from side surface109 to create a depression 825 in the side surface 109 of first bone 105to fit the head portion 103 of post member 101. Since the longitudinalaxis 516 of front surface of rasp portion 520 is offset from thelongitudinal axis 515 of pair of parallel bores 505 and 506 by angle D(FIGS. 5A-5B), the depression 825 is angled to receive the head portion103 in a flush configuration (FIG. 8E). In a preferred embodiment, thedepression 825 is created deep enough in first bone 105 such that thehead portion 103 sits within the depression 825 and is located below theside surface 109. The depth of depression 825 sets the depth thefixation assembly 100 is implanted into bones 105 and 106. To createdepression 825, instrument 500 is partially rotated or wiggled back andforth in directions D3 and D4 by rotating handle 502 manually, or byconnecting handle 502 to a torque transmitting tool (not shown).Rotating handle 502 rotates head portion 503 to scrape and remove bonematerial with teeth 521 of the rasp portion 520.

Next, in step 718, as shown in FIG. 8D, parallel bores 505 and 506 inhead portion 503 of the instrument are used to align a drill bit 833with first bone 105 to create third and fourth holes 831 and 832 infirst bone 105. To create the holes, the head portion 503 is alignedwith the first bone 105 and the drill bit 833 is inserted into each ofthe parallel bores 505 and 506 of head portion 503. In a preferredembodiment, third and fourth holes 831 and 832 are parallel and extendtransversely with respect to first bone 105. After the third and fourthholes 831 and 832 are created, in step 720, first and second legs 201and 202 are inserted into third and fourth holes 831 and 832,respectively, as shown in FIG. 8E. Head portion 103 is then pressed intothe depression 825 until it is flush with the cortex of the bone. Inalternative embodiments, post member 101 may be inserted by impaction,by press fit, by reaming, or substantially any other similar strategy ortechnique.

In step 722, the screw member 102 is advance over the K-wire 805, asshown in FIG. 8F, so that the K-wire guides the screw member 102 intofirst and second bones 105 and 106. Specifically, the K-wire 805 isinserted into bore 406 in the screw member 102, as shown in FIG. 8F.Screw member 102 is advanced through the bore 212 of the post member 101and through first and second holes 811 and 812 in the first and secondbones 105 and 106, respectively. Screw member 102 may be driven byinserting a torque transmitting tool into aperture 407 in the bulbousportion 403 and rotating the screw member 102, thereby engaging threads412 with the second bore 812 in the second bone 106. Screw member 102 isrotatably advanced into the second bone 106 until the tapered bulbousportion 403 engages and locks with tapered bore 212 in head 103 of thepost member 101. Finally, the K-wire 805 is removed from bones 105 and106 and the incision is closed.

As will be apparent to those skilled in the art, numerous variations maybe practiced within the spirit and scope of the present invention. Forexample, a variety of different tools—screw drivers, wrenches, reductioninstruments and drill guides—may be used in the practice of theinvention. Fixation assemblies of different sizes and different shapesmay be used. Likewise, different thread sizes and configurations may beused. There may also be variation in the procedure used to implant thefixation assembly in the bones. Certain steps can be omitted or combinedwith other steps and certain steps can be performed in a differentorder. For example, in some procedures it may not be necessary to use aK-wire or pre-drill holes in the bones.

While the invention has been described with reference to the preferredembodiment and alternative embodiments, which embodiments have been setforth in considerable detail for the purposes of making a completedisclosure of the invention, such embodiments are merely exemplary andare not intended to be limiting or represent an exhaustive enumerationof all aspects of the invention. The scope of the invention, therefore,shall be defined solely by the following claims. Further, it will beapparent to those of skill in the art that numerous changes may be madein such details without departing from the spirit and the principles ofthe invention. It should be appreciated that the invention is capable ofbeing embodied in other forms without departing from its essentialcharacteristics.

What is claimed is:
 1. A fixation assembly for bone or bone fragments,comprising: a post member comprising an elongated body extending from afirst end to a second end, wherein the post member comprises a headportion at the first end and an anchoring portion at the second end,wherein the anchoring portion comprises a first leg and a second legextending from the head portion and configured for insertion into afirst bone or first bone fragment, wherein the first leg and second legare each substantially straight and substantially parallel to each otherand to a first longitudinal axis, wherein the head portion extends alonga single second longitudinal axis, wherein the first longitudinal axisand the second longitudinal axis define a first angle, wherein the headportion comprises a partial ring annularly extending from a first end toa second end, and wherein the first leg extends from the first end ofthe partial ring and the second leg extends from the second end of thepartial ring; and a screw member extending from a first end to a secondend along a third longitudinal axis, the screw member comprising abulbous part at the first end, wherein the screw member couples to thepost member such that the first and the third longitudinal axes define asecond angle.
 2. The fixation assembly of claim 1, wherein the screwmember couples to the post member by inserting the screw member into thehead portion of the post member until the bulbous portion of the screwmember abuts the head portion of the post member.
 3. The fixationassembly of claim 1, wherein at least one of the first angle and thesecond angle is less than 90 degrees.
 4. The fixation assembly of claim1, wherein the first angle is in the range of about 30 degrees to about75 degrees.
 5. The fixation assembly of claim 1, wherein the first angledetermines the second angle of fixation of the post member with respectto the screw member.
 6. The fixation assembly of claim 1, wherein thesecond angle is in the range of about 15 degrees to about 60 degrees. 7.The fixation assembly of claim 1, wherein the fixation assembly iscapable of translating uniform compression to the first bone and asecond bone or the first bone fragment and second bone fragment.
 8. Thefixation assembly of claim 1, wherein at least one of the post memberand the screw member comprises a unitary elongated body.
 9. The fixationassembly of claim 1, wherein at least one of the post member and thescrew member comprises material selected from the group consisting oftitanium, titanium alloy, stainless steel, cobalt chrome, PEEK,resorbable polyactic acid, osteoconductive material, plasma spray, andany combination thereof.
 10. The fixation assembly of claim 1, whereinat least one of the head portion of the post member and the bulbousportion comprises a taper for providing an interference fit.
 11. Thefixation assembly of claim 10, wherein the taper comprises a Morsetaper.
 12. The fixation assembly of claim 1, wherein the anchoringportion is capable of being fixed transversely to a bone or a bonefragment.
 13. The fixation assembly of claim 1, wherein the screw memberis capable of being fixed diagonally to the first bone and a second boneor to the first bone fragment and a second bone fragment.
 14. Thefixation assembly of claim 1, wherein the first and second legs aresubstantially cylindrical in shape.
 15. The fixation assembly of claim1, wherein the first leg terminates at a first tip and wherein thesecond leg terminates at a second tip.
 16. The fixation assembly ofclaim 15, wherein each of the first and second tips comprises a conicalshape.
 17. The fixation assembly of claim 1, wherein the fixationassembly is capable of being implanted below the cortex of a bone.
 18. Afixation assembly comprising: a post member comprising a head portionconnected to an anchoring portion, wherein the head portion extendsalong a single axis and is joined to the anchoring portion at a firstangle, wherein the head portion comprises a curved body annularlyextending from a first end to a second end, wherein the first end isseparated from the second end by a slot, wherein the curved body definesan annular bore therein, wherein the anchoring portion comprises a firstleg extending from the first end of the curved body at the first angle,and a second leg extending from the second end of the curved body at thefirst angle and configured for insertion into a first bone or a firstbone fragment; and a screw member comprising an elongated portionconnected to a bulbous portion that couples with the curved body of thepost member, wherein the screw member is configured for insertion, anduniform compression of, the first bone and a second bone or the firstbone fragment and a second bone fragment.